What is the propagation delay in a digital circuit?

What is the propagation delay in a digital circuit?

• A. Propagation delay
• B. Rise time
• C. Fall time
• D. Bandwidth

Answer: (A)

Propagation delay is the time interval between when the input signal changes and when the output shows that change. It is typically measured from the 50% point of the input transition to the 50% point of the output transition, and there can be different values for rising and falling transitions (tpLH and tpHL). This delay comes from the time required for transistors to switch and for charge to move through the circuit’s capacitances, so it sets how quickly a gate or circuit can respond to a change. Rise time and fall time describe how fast the output moves from low to high or high to low (the transition speed), not the delay from input to output. Bandwidth relates to the range of frequencies the circuit can handle and is a broader, frequency-domain measure rather than the actual propagation delay.

Propagation delay is the time interval between when the input signal changes and when the output shows that change. It is typically measured from the 50% point of the input transition to the 50% point of the output transition, and there can be different values for rising and falling transitions (tpLH and tpHL). This delay comes from the time required for transistors to switch and for charge to move through the circuit’s capacitances, so it sets how quickly a gate or circuit can respond to a change. Rise time and fall time describe how fast the output moves from low to high or high to low (the transition speed), not the delay from input to output. Bandwidth relates to the range of frequencies the circuit can handle and is a broader, frequency-domain measure rather than the actual propagation delay.